Neo-functionalisation of the flowering pathway for vegetative storage-organ formation in potato

Abstract:

Potato reproductive development is regulated by the sensing of environmental cues resulting in the activation of a signalling cascade. Signal molecules synthesised in the perceiving organs are transported to the cells and tissues that go on to develop into flowers or tubers. Although soil nutrients and factors such as water availability and ambient temperature are important signals for reproductive development, the major environmental component for tuberisation is day-length. Transition from long to short days also influences important agronomic traits such as earliness and maturity. A major-effect QTL for Plant Maturity and Earliness in potato has been mapped on Chromosome 5 in diploid clones and in tetraploid material. Using map based cloning together with deep bi-allelic sequencing of chromosome 5, we have identified a gene coding for a central regulator underlying this major-effect QTL. We show that this gene, named StCDF1, belongs to the family of DOF transcription factors that regulates tuberisation and plant life-cycle length, by acting as a mediator between the circadian clock and the mobile tuberisation signal StSP6A. We have shown that naturally occurring allelic variants of this protein, evade post-translational regulation, thereby leading to early tuber formation and shortened life-cycle. We propose that this allelic variation has allowed the cultivation of potato outside the Andean centre of origin, under long-day conditions of spring and summer that prevail during the growing season in northern temperate latitudes.